Pokémon Mystery Dungeon: Explorers of Sky (Japanese: ポケモン不思議のダンジョン 空の探検隊Pokémon Mystery Dungeon: Explorers of Sky) is a game developed by Chunsoft, and is a sister game to Pokémon Mystery Dungeon: Explorers of Time and Explorers of Darkness. The game was first announced in CoroCoro, which released the first details in January 2009. It was officially released in Japan on April 18, 2009 and in North America on October 12th, 2009.

There is a new place called Spinda's Café where the following can be found:

Spinda's Juice Bar grants access to several exclusivedungeons, and it also allows players to make drinks out of food items.

Recycle Shop allows players to exchange excess items for other items. The more items exchanged, the better the items available will be. Players may also trade items for Prize Tickets (more kinds of tickets can be unlocked by team's rank, for example Silver Tickets are only available to teams in the Silver rank). Prize tickets can be used in a lottery, where the player gets to choose from three colors for the drawing (red, blue, and yellow). The player can sometimes get rare items this way.

The player's team recruits can now be found in Spinda's Café (once it opens).

Job requests can also be found here, and can be accepted or rejected by talking to the client to the left of the exit.

Dungeons that were previously only attainable through job requests can also be found in Spinda's Juice Bar and the Recycle Shop.

There is a new location called the Secret Bazaar which is found randomly in dungeons. It is run by Kirlia. The bazaar has several stalls found inside.

Lickilicky's will clean the player's items in their inventory for 100 Poké.

Shedinja's gives players a chance to escape the dungeon sooner for 100 Poké.

A new location, Shaymin Village, is unlocked after completion of the main game, featuring a tribe of Shaymin, where the player also allies with Team Frontier to reclaim the trail leading to the top of the nearby Sky Peak mountain. An accompanying Shaymin demonstrates its ability to instantly purify polluted environments, its use of the Gracidea to transform into its Sky Forme, and can be later recruited into the player's party.

Players can find a statue of Arceus in a new dungeon called Destiny Tower. The story here involves a new item called the Space Globe.

Players only lose half of their money when defeated in a dungeon, instead of all of it.

Tradeable items can be traded for any others now, provided they are available at Croagunk's Swap Shop.

Using DS Download Play, the player can send their friends a demo of the game.

Jirachi is now fought in Star Cave, only accessible through Wonder Mail codes or Spinda's Café. The Special Episode "Bidoof's Wish" must be completed first.

Occasionally bottles containing job requests will wash up along the beach. Upon finding a bottle the player has the option to take or reject the request. Rejected jobs remain on the beach until taken. However, if the player wants, they can accept the job and then delete it to remove the bottle.

Some of the items found in a dungeon might not be what they seem to be. These items are called Lookalike items. For example, a blue Berry found in a dungeon might not be of the healing Oran variety, but the damaging Oren.

Other minor differences with Time and Darkness

When the player robs a Kecleon in Time/Darkness he says "Robbed! I've been robbed! Catch the thief!". In Sky, he says, "My precious merchandise! Catch the thief!" instead.

When the player recruits a new Pokémon, if the team is full, it allows the player to choose who they would like to send back to the guild, instead of immediately sending the new recruit back. Likewise, the same goes if the player tries to do an escort mission and the team is full.

The amount of time it takes to save the player's game is much shorter.

When saving their game, the player can choose whether they want to continue playing or return to the main menu.

When the team's leader tries to switch places with a teammate while they are on a terrain the teammate cannot normally walk on, the teammate will warp right back to them, whereas in previous games it would warp them to a random spot.

Plot

The story begins with the player having been washed ashore by a storm. Meanwhile, the partner is nervous about joining the Wigglytuff's Guild, a local exploration club, and gives up early. Walking along the beach, the partner encounters the player, and informs that the player has been turned into a Pokémon. The Relic Fragment is stolen by Zubat and Koffing, members of Team Skull, which the player helps recover. After a brief exchange the partner explains their motivation for joining the guild, the partner loves legend and lore and their life dream is to find what their personal treasure, the Relic Fragment belongs to. The partner, reinvigorated by the player's courage, joins the Guild as a new team with the player.

Over the next few days, the team gets accustomed to life at the Guild and the nearby Treasure Town. Among the folks they meet are Wigglytuff, the kindhearted Guildmaster, Chatot, the hot-tempered yet well-meaning second-in-command, Bidoof, the newest recruit prior to the team joining, the Guild Chef Chimecho (also in charge of maintaining the team), Diglett and Loudred, the Guild sentries, Dugtrio, maintainers of the job boards, Magnezone, the local sheriff, and other exploration teams. As they are introduced to the Guild, they learn of the fact that rogue Pokémon have been wreaking havoc in the world due to the disruption of time, Pokémon cannot evolve, and new "Mystery Dungeons" have been revealed and open to exploration.
The player discovers not too long after that he/she has the ability to spontaneously see things in the past and future, which is known as the Dimensional Scream.

Special episodes

During the course of the game, players can engage in various scenarios that expand upon the story of some of the different characters.